Out of round mandrel???

[lobster]

I'm so new to this pen turning deal I'm not sure if I have a problem or not.

It seems there is a vibration with my PSI mandrel. I can't quite get the rod to keep from visibly turning out of round out by the end (at the threads). I haven't measured it, but I would estimate ~0.5mm...enough to been seen slightly and certainly felt.

I tried using the same mandrel in a different lathe and seemed to get the same result. That tells me the mandrel is perhaps bent slightly...

However...

If I take the rod out of the mandrel and roll it across the cast iron top of the table saw, it doesn't roll "cupped". I also took the rod out of the chuck portion of the mandrel and chucked it up in the drill press and it seemed to spin smoother than on the lathe. What the heck?

The lathe a turn pens on is a Jet 1014 non VS. The tail stock center lines up very well with a drive spur center.

Mandrels are cheap...should I just go buy another one to see if I have the same issue? Maybe I should buy a better one...that is...not from PSI? Any advice would be appreciated.

 

[bobleibo]

I'm so new to this pen turning deal I'm not sure if I have a problem or not.

It seems there is a vibration with my PSI mandrel. I can't quite get the rod to keep from visibly turning out of round out by the end (at the threads). I haven't measured it, but I would estimate ~0.5mm...enough to been seen slightly and certainly felt.

I tried using the same mandrel in a different lathe and seemed to get the same result. That tells me the mandrel is perhaps bent slightly...

However...

If I take the rod out of the mandrel and roll it across the cast iron top of the table saw, it doesn't roll "cupped". I also took the rod out of the chuck portion of the mandrel and chucked it up in the drill press and it seemed to spin smoother than on the lathe. What the heck?

The lathe a turn pens on is a Jet 1014 non VS. The tail stock center lines up very well with a drive spur center.

Mandrels are cheap...should I just go buy another one to see if I have the same issue? Maybe I should buy a better one...that is...not from PSI? Any advice would be appreciated.

It takes very little for a mandrel to bow, usually from over-tightening the nut or the tailstock. I have a tendancy to do that so I use only the adjustable ones and turn one blank at a time using only enough of the rod to get the blank and 2 spacers on at a time. That reduces the chances of bowing. As inexpensive as the replacement rods are, I keep a few new ones at hand and change them often, especially when I think I may have one out of round. I've had pretty good luck with the stainless ones. A $4 rod is a lot less expensive than the time and cost of the blank that might get ruined.
Good luck....

 

[randyrls]

It seems there is a vibration with my PSI mandrel. I can't quite get the rod to keep from visibly turning out of round out by the end (at the threads). I haven't measured it, but I would estimate ~0.5mm...enough to been seen slightly and certainly felt.

Larry; Check the tail stock point. The standard wood lathe tail stock has a very sharp point on the live center. BUT; for turning with a mandrel the point needs to be a 60 degree live center. Like this

You want the point to "ride" on the outside rim of the hole in the mandrel. You can either drill the hole in the mandrel rod deeper, or file the point off the tail stock. If the tip of the tail stock is bent over, that is a sure sign.

Hope this helps.

 

[mbroberg]

I haven't used a mandrel in quite a few months but the 1st question I have is how are your pens turning (pardon the pun) out. Are they out of round?

If you haven't invested a lot of money in bushings yet consider ditching the mandrel all together. George (Texatdurango) just posted some real good information on one way of turning between center instead of with a mandrel. Check it out at
http://www.penturners.org/forum/showthread.php?t=54760

 

[KenBrasier]

From what you describe, I'd initally look at two or three things. 1.) is the countersink in the end of the mandrel possibly off-center. If you don't engage the live center, does it rotate true? 2.) Is there any play in your live center? 3.) Are you getting your live center snugly in the countersink of the mandrel to avoid wobble?

 

[Seer]

I have been using the woodcraft mandrel and nothing but issues, my fault most likeley. I bought the adjustable for 23.00 with the 10.00 discount and just used it today to fix an out of round cigar I turned, I turned one barrel at a time and it was so much nicer using it this way ( I am waiting ot go mandrelles) no vibration and smooth. Pen is good now.

 

[leehljp]

AS already mentioned or asked: Are you using a 60° Live Center on the tail stock? Or the stock center that came with the lathe?

Most people new to pen turning do not realize that a 60° live center in the tail stock is a NECESSITY for use with a MANDREL. Otherwise there will be problems.

Bringing up the Tail Stock too tight will cause that also. Sometimes, this is overlooked.

A third possibility is out of round (OOR) or Off Center (OC) drilled bushings. This is more common than many people realize. If you have calipers, measure them.

 

[witz1976]

This is a new live center for the tail stock that is "designed" to prevent all the issues of bent mandrels. Seems pretty cool...
http://www.pennstateind.com/store/PKMSTS2.html

 

[leehljp]

This is a new live center for the tail stock that is "designed" to prevent all the issues of bent mandrels. Seems pretty cool...
http://www.pennstateind.com/store/PKMSTS2.html

That is a nice looking live center for sure. But it will not prevent bent mandrels. What it will prevent is the wobble that is caused from sticking the lathe's stock live center into the end of the mandrel.

Bent mandrels comes from other forces prior to mounting it between the head stock and tail stock. If a bent mandrel occurs while mounted, either with that TS or the non-60° center (or even a 60°) it is because of an accidentally hard bump.

That mandrel will prevent the wobble that is common from using stock live centers. I see this as PSI's answer to prevent people from going TBC. Mandrel usage increases hardware sales far more than TBC/mandrel-less . . . not pen turning accuracy.

TBC - where less parts increases the ability for accuracy and costs less in the long run.

 

[mywoodshopca]

Few times during the final turning, turn off the lathe and turn the blank a little on the rod then tighten back up.. This will help "trim" down the OOR sides as well.. I still use mandrel and tend to turn mine 2-3 times during the process and dont have much OOR problems.

 

[dogcatcher]

This is a new live center for the tail stock that is "designed" to prevent all the issues of bent mandrels. Seems pretty cool...
http://www.pennstateind.com/store/PKMSTS2.html

That won't fix the problem, if the mandrel is bent, it is bent, no live center regardless of the configuration will fix it. This live center also will not prevent someone from bending or bowing the mandrel. Good gimmick, but not the miracle they think it is.

 

[wb7whi]

Ok, al lot of information but I think there is another point that can be addressed. Put the mandril in the headstock and bring up the tailstock to where the live center is not quite touching the mandril.
Turn the mandril (headstock) by hand watching how the tip of the mandril relates to the tip of the live center. If the tip of the madril runs high and low to the tip of the live center your mandril is bent.
To true it up turn the mandril to the highspot then grab the mandril and gently bend it to the low spot. Keep checking and gently bending until the mandril is running true.

Caution; you maybe new but you are already addicted. Good luck.

 

[KenV]

One more thing to check == crud in the headstock taper or on the MT 2 taper will cause the headstock end of the mandrell to be excentric and sure enough the tailstock end will be too. That would account for a straight mandrel acting in an excentric manner.

One chip will do it (been there and found that --)

 

[Ray McLeod]

Out of Round

You mentioned that the out of round was at the threads...I had an incident with an out of round because I had the bushing on the threads instead of the unthreaded mandrel. There was play on the threads...Ray

 

[bobleibo]

Some great tips here that I will put in my bag of tricks. One other way to check that I use while my lathe is running is to let my skew ride very lightly on the edge on top of the rod itself and then on top of the bushing. If there is any chatter whatsoever, they are out of round.
Good luck......

 

[lobster]

Thanks for all the info. I will try some of these and get back to you. I do not have a dedicated 60 degree tail stock live center. I was using the one which came with the lathe. Although, I did look at it closely and it appears the point of the tail stock is not getting bent...but you never know.

Thanks all.